(a) Field of the Invention
The present invention relates to an automatic transmission for a vehicle and more particularly, to a planetary gear train of an automatic transmission for a vehicle that minimizes complexity, realizing at least ten forward speeds, improves power delivery performance and fuel consumption due to multi-stages, and improves driving stability of a vehicle by utilizing a low rotation speed of an engine.
(b) Description of the Related Art
Generally, in the automatic transmission field achieving a greater number of shift stages is a technology that maximizes fuel consumption and driving efficiency and has been researched, to reduce fuel consumption of a vehicle. In particular, research regarding an engine has been concluded to reduce the weight of the vehicle and to improve fuel efficiency and thereby reduce fuel consumption. Further research regarding an automatic transmission has been conducted to simultaneously improve drivability and fuel consumption by achieving a greater number of shift stages.
For example, to achieve more shift stages for an automatic transmission, the number of components, particularly the number of planetary gear sets is typically increased and installability, production cost, weight, and/or power flow efficiency according to total length of transmission is increased. Therefore, in order to maximally enhance fuel consumption of an automatic transmission having more shift stages, improved efficiency must include a smaller number of components. Recently, an eight-speed automatic transmission has been introduced and a planetary gear train for an automatic transmission enabling more shift stages is continuously required.
However, the majority of general automatic transmissions have more than eight speeds and typically include three to four planetary gear sets and five to six control elements (e.g., friction element). In other words, the total length is increased, which has drawbacks including deterioration of installability. As a result, multiple rows structure which planetary gear sets are on planetary gear sets have been adopted or in other words a dog clutch has been applied in place of wet control elements. However, applicable structure is restricted and shift feel deteriorates by application of the dog clutch.
The above information disclosed in this section is merely for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.